Bottom-up regulation of plant community structure in an aridland ecosystem

We conducted a long-term rodent exclosure experiment in native grass- and shrub-dominated vegetation to evaluate the importance of top-down and bottom-up controls on plant community structure in a low-productivity aridland ecosystem. Using multiple regressions and analysis of covariance, we assessed how bottom-up precipitation pulses cascade through vegetation to affect rodent populations, how rodent populations affect plant community structure, and how rodents alter rates of plant community change over time. Our findings showed that bottom-up pulses cascade through the system, increasing the abundances of plants and rodents, and that rodents exerted no control on plant community structure and rate of change in grass-dominated vegetation, and only limited control in shrub-dominated vegetation. These results were discussed in the context of top-down effects on plant communities across broad gradients of primary productivity. We conclude that bottom-up regulation maintains this ecosystem in a state of low primary productivity that constrains the abundance of consumers such that they exert limited influence on plant community structure and dynamics.     

Theory into Practice: Implementing Ecosystem Management Objectives in the USDA Forest Service

In the United States and around the world, scientists and practitioners have debated the definition and merits of ecosystem management as a new approach to natural resource management. While these debates continue, a growing number of organizations formally have adopted ecosystem management. However, adoption does not necessarily lead to successful implementation, and theories are not always put into practice. In this article, we examine how a leading natural resource agency, the United States Department of Agriculture Forest Service, has translated ecosystem management theory into concrete policy objectives and how successfully these objectives are perceived to be implemented throughout the national forest system. Through document analysis, interviews, and survey responses from 345 Forest Service managers (district rangers, forest supervisors, and regional foresters), we find that the agency has incorporated numerous ecosystem management components into its objectives. Agency managers perceive that the greatest attainment of such objectives is related to collaborative stewardship and integration of scientific information, areas in which the organization has considerable prior experience. The objectives perceived to be least attained are adaptive management and integration of social and economic information, areas requiring substantial new resources and a knowledge base not traditionally emphasized by natural resource managers. Overall, success in implementing ecosystem management objectives is linked to committed forest managers.     

Early prenatal sonographic appearance of rare thoraco-abdominal eventration

Fetal ventral wall malformations may be diagnosed prenatally with ultrasound. These include omphalocele, gastroschisis, or even thoracic defects with or without ectopia cordis. It is important whenever such a defect is found to carefully define the full extent of the lesion prior to parental counselling. Described and illustrated here is the prenatal diagnosis with real-time ultrasound at 17 weeks gestation of a rare thoraco-abdominal ventral wall defect including omphalocele, bifid sternum, diaphragmatic aplasia, and pericardial aplasia with incomplete ectopia cordis. The technique is described and the importance of the complete, accurate delineation of anatomic malformations is emphasized.     

Causes and Consequences of Backdrafting of Vented Gas Appliances

Abstract

House depressurization occurs when household equipment such as a kitchen or bathroom fan or a fireplace exhausts air from the house and lowers the pressure indoors with respect to the outside. The operation of air handlers for forced-air heating or cooling systems also can have a depressurization effect. This depressurization can hinder the natural draft from vented combustion appliances and lead to backdrafting, which in turn can result in combustion gases spilling into the indoor airspace. Extensive spillage can cause elevated indoor levels of combustion products such as carbon dioxide (CO2) and water vapor, as well as contaminants such as carbon monoxide (CO) and nitrogen dioxide (NO2).

The focus of this paper is to review studies on depressurization- induced backdrafting and spillage from gas-fired, drafthood equipped furnaces and domestic hot water heaters. Qualitative and quantitative techniques that were used in depressurization and backdrafting studies conducted in Canada, Europe, and the United States are analyzed. These studies have shown that exhaust fans operated simultaneously with fireplaces depressurize houses by 3 to 8 Pa on average. The CO indoor concentrations due to spillage, as reported in these studies, generally have been lower than 5 ppm. However, such low CO concentrations do not necessarily imply that a potential problem associated with backdrafting does not exist. Other combustion products, such as NO2, rarely have been measured in prior backdrafting studies.

It can be concluded from the literature review that causes of house depressurization are well understood. However, more comprehensive research is needed to better understand the frequency, duration, and severity of depressurization-induced spillage in a broad cross section of houses. Efforts in this direction have begun recently in the United States through a workshop to define research issues, pilot studies to develop comprehensive measurement protocols, and consensus standard development activities to prepare standardized methods and protocols.     

Community Responses to Government Defunding of Watershed Projects: A Comparative Study in India and the USA

When central governments decentralize natural resource management (NRM), they often retain an interest in the local efforts and provide funding for them. Such outside investments can serve an important role in moving community-based efforts forward. At the same time, they can represent risks to the community if government resources are not stable over time. Our focus in this article is on the effects of withdrawal of government resources from community-based NRM. A critical question is how to build institutional capacity to carry on when the government funding runs out. This study compares institutional survival and coping strategies used by community-based project organizations in two different contexts, India and the United States. Despite higher links to livelihoods, community participation, and private benefits, efforts in the Indian cases exhibited lower survival rates than did those in the U.S. cases. Successful coping strategies in the U.S. context often involved tapping into existing institutions and resources. In the Indian context, successful coping strategies often involved building broad community support for the projects and creatively finding additional funding sources. On the other hand, the lack of local community interest, due to the top-down development approach and sometimes narrow benefit distribution, often challenged organizational survival and project maintenance.     

Population activity patterns — St. Louis study

In the context of exposure monitoring, activity patterns refer to the manner in which individuals' activities are distributed in time, in space, and by environmental mode. The background and design are given for a cross-sectional survey conducted in the St. Louis area during 1978–1979. Activity pattern estimates from the study, based on a combination of usual frequency and diary methods, are presented and their limitations are discussed. Methods for and the types of estimates from national studies employing time-use diaries are presented. Considerations for activity pattern recording during future monitoring studies are provided.     

Reducing Nonpoint Source Pollution Through Collaboration: Policies and Programs Across the U.S. States

Nonpoint source (NPS) pollution has emerged as the largest threat to water quality in the United States, influencing policy makers and resource managers to direct more attention toward NPS prevention and remediation. In response, the United States Environmental Protection Agency (USEPA) spent more than $204 million in fiscal year (FY) 2006 on the Clean Water Act’s Section 319 program to combat NPS pollution, much of it on the development and implementation of watershed-based plans. State governments have also increasingly allocated financial and technical resources to collaborative watershed efforts within their own borders to fight NPS pollution. With increased collaboration among the federal government, states, and citizens to combat NPS pollution, more information is needed to understand how public resources are being used, by whom, and for what, and what policy changes might improve effectiveness. Analysis from a 50-state study suggests that, in addition to the average 35% of all Section 319 funds per state that are passed on to collaborative watershed groups, 35 states have provided financial assistance beyond Section 319 funding to support collaborative watershed initiatives. State programs frequently provide technical assistance and training, in addition to financial resources, to encourage collaborative partnerships. Such assistance is typically granted in exchange for requirements to generate a watershed action plan and/or follow a mutually agreed upon work plan to address NPS pollution. Program managers indicated a need for greater fiscal resources and flexibility to achieve water quality goals.     

Citizen Participation in Collaborative Watershed Partnerships

Collaborative efforts are increasingly being used to address complex environmental problems, both in the United States and abroad. This is especially true in the growing field of collaborative watershed management, where diverse stakeholders work together to develop and advance water-quality goals. Active citizen participation is viewed as a key component, yet groups often struggle to attract and maintain citizen engagement. This study examined citizen participation behavior in collaborative watershed partnerships by way of a written survey administered to citizen members of 12 collaborative watershed groups in Ohio. Results for the determination of who joins such groups were consistent with the dominant-status model of participation because group members were not demographically representative of the broader community. The dominant-status model, however, does not explain which members are more likely to actively participate in group activities. Instead, individual characteristics, including political activity, knowledge, and comfort in sharing opinions with others, were positively correlated with active participation. In addition, group characteristics, including government-based membership, rural location, perceptions of open communication, perceptions that the group has enough technical support to accomplish its goals, and perceived homogeneity of participant opinions, were positively correlated with active participation. Overall, many group members did not actively participate in group activities.     

Genetic Diversity and Tests of the Hybrid Origin of the Endangered Yellow Larkspur

Abstract: Delphinium luteum ( Ranunculaceae), an endangered larkspur, is restricted to two wild populations near Bodega Bay, California. The total number of individuals in these two populations is estimated to be <100. We used allozyme and random amplified polymorphic DNA ( RAPD) markers to (1) assess levels and patterns of genetic diversity in one wild population and two cultivated populations and (2) test the hypothesis that D. luteum is of hybrid origin between D. decorum and D. nudicaule . These data will be used to aid in developing a management plan to conserve the species. The wild population maintains high levels of genetic diversity. Genetic data indicate that both cultivated populations, especially the north Sonoma population, have several allozymes and RAPD markers not found in the wild population and could be used to establish new populations of D. luteum or to enhance the diversity and size of the wild population. The allozyme data did not reveal any fixed differences between D. decorum and D. nudicaule , although allele frequencies of the putative parental populations differed. At these loci, D. luteum resembled D. nudicaule more than D. decorum  . Many unique RAPD markers distinguish each of the three species. The diagnostic markers from populations of D. nudicaule and D. decorum were not additive in the putative hybrid, and these data indicate that D. luteum is not of recent hybrid origin. Conservation of the yellow larkspur should include strategies that use the cultivated populations of D. luteum , but hybridizing D. decorum and D. nudicaule to "recreate" D. luteum is not recommended.